Hi,
A generic 4 wire bosch O2 sensor has a black , a grey, and two white wires.

How do you know what way to connect the white wires?

Does it matter which way the white wires are connected?

There are no markings on them to distinguish one from the other...

Rich

You have to be a trained professional to know which white wire is which. Faling that, you could just hook them up, one to 12V+ and one to ground, and that'll work just fine ................................ The Cap'n

I know they are part of the pre-heater thing...

So, oh mighty capn, would you care to share the secret handshake...

I put a generic one in my car...I still get the code...

Its the rear sensor...the OEM part is also a splic in version...same bosch #, but 3 times the price.

The OEM one, book, says to use crimp connectors...I did.
I was thinking of going back in and solder the connection instead...may be some voltage loss.

So I got a generic 4 wire...

The code keeps coming back.

If I wired it backwards, would it matter?

Rich

If you mix the grey and black wires, you have a problem (one is signal ground, the other is the signal itself). The two white wires are the heater, and they're not polarized. Connect one to switched +12, the other to ground, and you're fine. You basically can't hook up the heater backwards.

Thanx
I was not getting a clear answer ...
I love this place..

Oh,
I have heard differing opinion on using crimp connectors versus soldering/heat shrink..

what is the right way?

Rich

Crimp and heatshrink.

Soldering is bad for anything that's going to vibrate, as it makes the wires brittle. This is my opinion, and the opinion of those who set standards in the aerospace industry. Not everyone agrees with it.